A typical image display apparatus includes a display section formed of a number of display units arranged vertically and horizontally, and each of the display units is provided by arranging, in a grid pattern, pixels each formed of a light-emitting element such as an LED. To increase the resolution of the image display apparatus, it is necessary to reduce the pitch of the arranged pixels to arrange the pixels at a higher density. A large image display apparatus with a high resolution tends to have a higher cost due to the use of an increased number of LED elements per unit area.
An example of the large image display apparatus displays full-color images by having a display section formed such that pixels at least including an LED element for R (red), an LED element for G (green), and an LED element for B (blue) are arranged in a grid pattern on a basic grid (square grid) consisting of four pixels of a 2 by 2 matrix. For example, in the four pixels of the basic grid (square grid) consisting of the 2 by 2 matrix, an LED element for each of R, G, and B is assigned to three pixels, and G or R is assigned to the remaining one pixel.
The LED element allows arbitrary design of arrangement of three primary colors or arrangement pitch, which contributes to a recent selection of image display apparatuses with various resolution and luminance levels appropriate for different applications.
In another display type used in recent years, a three-in-one LED element (three-in-one element) including LED chips for three colors of R, G, and B put in a single LED lamp is used, and such three-in-one elements are arranged in a grid pattern.
When LED elements of the three-in-one type are arranged as pixels, one pixel emits light of three primary colors and thus the three colors are easily mixed as compared with a type in which single-color LED elements for R, G, and B are arranged. This provides a characteristic in which a viewer recognizes a mixed color at a shorter distance.
Various types of LED arrangement include the following ones including the LED element of the three-in-one type.
In recent years, applications requiring viewing at a shorter distance or applications requiring display with a higher resolution have increasingly employed a three-in-one element in which an LED pellet for three colors R, G, and B constitutes a single pixel (see, for example, Patent Document 1).
When the three-in-one element is used, an application requiring display of high-resolution contents with high image quality, for example Hi-Vision, involves a higher density of arrangement of LED elements, so that the cost is drastically increased and consumed power tends to be increased.
A proposed approach to reducing the cost is to reduce the number of LED elements while a reduction in image quality is minimized (see, for example, Patent Document 2).
Another proposed approach is to replace some of three-in-one LED elements with inexpensive white-color LED elements in a display having an array of three-in-one LED elements (see, for example, Patent Document 3).
As another example of the use of the white-color LED element, a recently proposed approach in the field of liquid crystal displays is to use four sub-pixels for colors of R, G, B, and W for a representative LED pixel arrangement of liquid crystal consisting of three colors of R, G, and B (see, for example, Patent Document 4).